In a communication system such as WCDMA (Wideband Code Division Multiple Access), LTE (Long Term Evolution), or LTE-A (LTE-Advanced) by 3GPP (Third Generation Partnership Project) or Wireless LAN or WiMAX (Worldwide Interoperability for Microwave Access) by IEEE (The Institute of Electrical and Electronics Engineers), a base station (cell, transmitter station, transmission apparatus, eNodeB) and a terminal (mobile terminal, receiver station, mobile station, reception apparatus, User Equipment (UE)) are respectively provided with a plurality of transmit/receive antennas and spatial-multiplex data signals by using a MIMO (Multi Input Multi Output) technique to realize high-speed data communication.
In order to realize the data communication between the base station and the terminal in such a communication system, the base station performs various kinds of control on the terminal. Therefore, the base station provides control information to the terminal by using a predetermined resource and thus performs downlink and uplink data communication. For example, the base station realizes the data communication by providing resource assignment information, data signal modulation and coding information, data signal spatial multiplexing number information, transmission power control information and the like to the terminal. For such control information, it is possible to use a method disclosed in NPL 1.
In addition, it is possible to use various methods as a communication method using the MIMO technique in the downlink, and for example, a multi user MIMO scheme in which the same resource is assigned to different terminals or a Cooperative Multipoint, Coordinated Multipoint (COMP) scheme in which a plurality of base stations cooperate to perform data communication can be used.
FIG. 37 is a diagram illustrating an example in which the multi user MIMO scheme is performed. In FIG. 37, a base station 3701 performs data communication with a terminal 3702 through a downlink 3704 and performs data communication with a terminal 3703 through a downlink 3705. Here, the terminal 3702 and the terminal 3703 perform data communication based on the multi user MIMO. In the downlink 3404 and the downlink 3705, the same resource is used. The resource is configured of resources in a frequency direction and a time direction. In addition, the base station 3701 controls beams with respect to each of the downlink 3704 and the downlink 3705 by using a pre-coding technique or the like and thus maintains mutual orthogonality or reduces the same channel interference. Accordingly, the base station 3701 can realize the data communication with the terminal 3702 and the terminal 3703 by using the same resource.
FIG. 38 is a diagram illustrating an example in which the downlink CoMP scheme is performed. FIG. 38 shows a case where a macro base station 3801 with wider coverage and a RRH (Remote Radio Head) 3802 with narrower coverage than that of the macro base station 3801 construct a radio communication system using a heterogeneous network configuration. Here, a configuration in which the coverage of the macro base station 3801 includes a part or an entirety of the coverage of the RRH 3802 will be considered. In the example shown in FIG. 38, the macro base station 3801 and the RRH 3802 construct the heterogeneous network configuration and cooperate to perform data communication with a terminal 3804 through a downlink 3805 and a downlink 3806, respectively. The macro base station 3801 is connected with the RRH 3802 via a connection 3803 and can transmit and receive control signals and data signals to and from the RRH 3802. For the connection 3803, it is possible to use wired connection such as an optical fiber or radio connection using a relay technique. Here, it is possible to improve total spectral efficiency (transmission capacity) in a coverage area constructed by the macro base station 3801 by a part or an entirety of the macro base station 3801 and the RRH 3802 respectively using the same frequency (resource).
The terminal 3804 can perform single cell communication with the base station 3801 or the RRH 3802 when positioned near the base station 3801 or the RRH 3802. Furthermore, the terminal 3804 is to prepare a counter measure for the same channel interference from the macro base station 3801 when positioned near an end (cell edge) of the coverage constructed by the RRH 3802. A method for reducing or suppressing interference of the cell edge region with respect to the terminal 3804 by using the COMP scheme, in which the macro base station 3801 and the RRH 3802 cooperate, as multi cell communication (cooperative communication, multi point communication, CoMP) between the macro base station 3801 and the RRH 3802 has been reviewed. As such a CoMP scheme, a method disclosed in NPL 2 has been examined.
FIG. 39 is a diagram illustrating an example in which the uplink CoMP scheme is performed. FIG. 39 shows a case where a macro base station 3901 with wide coverage and a RRH (Remote Radio Head) 3902 with narrower coverage than that of the macro station construct a radio communication system using the heterogeneous network configuration. Here, a configuration in which the coverage of the macro base station 3901 includes a part or an entirety of the coverage of the RRH 3902 will be considered. In the example shown in FIG. 39, the macro base station 3901 and the RRH 3902 construct the heterogeneous network configuration and cooperate to perform data communication with a terminal 3904 via an uplink 3905 and an uplink 3906, respectively. The macro base station 3901 is connected with the RRH 3902 via connection 3903 and can transmit and receive reception signals, control signals, and data signals to and from the RRH 3902. For the connection 3803, it is possible to use wired connection such as an optical fiber or radio connection using the relay technique. Here, it is possible to improve total spectral efficiency (transmission capacity) in a coverage area constructed by the macro base station 3901 by a part or an entirety of the macro base station 3901 and the RRH 3902 respectively using the same frequency (resource).
The terminal 3904 can perform single cell communication with the base station 3901 or the RRH 3902 when positioned near the base station 3901 or the RRH 3902. In such a case, if the terminal 3904 is positioned near the base station 3901, then the base station 3901 receives and demodulates a signal received via the uplink 3905. Alternatively, if the terminal 3904 is positioned near the RRH 3902, then the RRH 3902 receives and demodulates a signal received via the uplink 3906. Furthermore, if the terminal 3904 is positioned near an end (cell edge) of the coverage constructed by the RRH 3902 or near an intermediate point between the base station 3901 and the RRH 3902, then the macro base station 3901 receives the signal received via the uplink 3905, the RRH 3902 receives the signal received via the uplink 3906, the macro base station 3901 and the RRH 3902 then transmit and receive the signals received from the terminal 3904 via the connection 3903, synthesize the signals received from the terminal 3904, and demodulate the synthesized signal. An improvement in performance of the data communication by such processing is expected. This is a method called synthesized reception (JR: Joint Reception), and it is possible to improve the performance of the data communication in the cell edge region or the region near the intermediate point between the macro base station 3901 and the RRH 3902 by using the CoMP scheme in which the macro base station 3901 and the RRH 3902 cooperate as uplink multi cell communication (cooperative communication, multi point communication, CoMP).